1. Technical Field
Embodiments of the present invention generally relate to an image forming apparatus, such as a copier, a printer, a facsimile machine, or a multifunction peripheral (i.e., a multifunction machine) having at least two of copying, printing, facsimile transmission, plotting, and scanning capabilities.
2. Description of the Related Art
At present, image forming apparatuses such as printers and facsimile machines to output electronic data and copiers to copy documents are widely used. There are electrophotographic image forming apparatuses that form electrostatic latent images on an image bearer such as a photoconductor drum with laser beams, cause charged developer, such as toner, to adhere to the latent image, thereby developing the latent image into a toner image, transfer the toner image on a sheet of recording media, and fix the toner image on the sheet by heating and pressing the sheet.
When the toner image is transferred from the image bearer onto the sheet, a certain amount of toner remains on the image bearer. Accordingly, after image formation, such toner is removed by a cleaning device and collected in a waste-toner container. The collected toner may be still usable. Disposing the still usable toner is not desirable from the viewpoint of environment and running cost of the apparatus. Additionally, replacement frequency of the waste-toner container increases, thus making the maintenance and management of the apparatus more complicated.
Therefore, reuse of developer collected from the image bearer has been proposed. Reuse of collected developer is preferable since the amount of images produced with an identical amount of developer increases and the amount of waste developer is reduced.
Typical developer used in electrophotographic image forming apparatuses, however, is degraded while being exposed to heat, humidity, and outside air. Developer is also degraded by friction with a developer conveying mechanism, such as a developer conveying screw to spread developer inside a developing device in a main scanning direction. Therefore, developer supplied from an isolated developer bottle to the developing device is gradually degraded with time. The degradation progresses in proportional to increases in the amount of driving of the developer conveying mechanism. Depending on the degree of degradation, image quality is affected. For example, images become smeary, or toner is partly absent in images.
Although reuse of developer can reduce environmental impact, running cost of the apparatus, replacement frequency of waste-toner containers, thereby making the maintenance and management of the apparatus easier, it makes it difficult to guarantee image quality.
Thus, there is trade-off between advantages attained by reuse of developer and image quality guarantee.